Fix FreeList::zapFreedMemory to fail "use-of-uninitialized-value" on MSAN

Source/platform/heap/Heap.h

Index: Source/platform/heap/Heap.h
diff --git a/Source/platform/heap/Heap.h b/Source/platform/heap/Heap.h
index 2100b6ef2ae2681c330e16c85606fe0d3231d0df..2ca9d5b554124fcdf0f75c0599f958ca09adf8bb 100644
--- a/Source/platform/heap/Heap.h
+++ b/Source/platform/heap/Heap.h
@@ -78,7 +78,7 @@ const uint8_t reuseForbiddenZapValue = 0x2c;
 // memory is zeroed out when the memory is reused in Heap::allocateObject().
 // In production builds, memory is not zapped (for performance). The memory
 // is just zeroed out when it is added to the free list.
-#if ENABLE(ASSERT) || defined(LEAK_SANITIZER) || defined(ADDRESS_SANITIZER)
+#if ENABLE(ASSERT) || defined(LEAK_SANITIZER) || defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)

[Alexander Potapenko, 2015/07/27 09:39:20]

Note that ASAN_{POISON,UNPOISON}_MEMORY_REGION makes little sense in MSan builds
(unless you define it to poison/unpoison MSan shadow, in which case it needs to
be renamed).

 #define SET_MEMORY_INACCESSIBLE(address, size) \
     FreeList::zapFreedMemory(address, size);   \
     ASAN_POISON_MEMORY_REGION(address, size)